This invention relates to elevators, and in particular to systems and methods for detecting presence of a person on top of the elevator car, or a person in a hoistway above or below the car, or an open landing door with no elevator present at the landing.
Elevator safety systems have been developed to protect persons who may enter a hoistway and may be injured by movement of an elevator car within the hoistway. Elevator mechanics and building maintenance personnel may, on occasion, need to enter the hoistway either on top of an elevator car, or in the pit at the bottom of the hoistway.
When access to the top of the elevator car is required, a mechanic typically opens a hoistway door at the floor above the current location of the car and climbs onto the top of the car to perform an inspection, maintenance, or repair. An inspection switch is typically provided on the top of the car, so that the mechanic can prevent the car from making unexpected movements.
Access to the pit area is typically obtained by opening the hoistway doors at the lowest landing floor, while the elevator car is located at a higher floor in the hoistway. A pit emergency switch may be provided so that the mechanic entering the pit can disable movement of the elevator car downward into the pit while the mechanic is working in the pit.
Elevator safety systems must also take into account the potential for unauthorized persons gaining entrance to the hoistway. Elevator surfers have found ways to bypass safety installations and gain access to the hoistway of an elevator, so that they can ride on top of the elevator car as it travels up and down within the hoistway.
Elevator safety systems typically make use of a safety chain that includes hoistway door contacts on each hoistway door that are connected in series with the power supply and drive motor of the elevator. The top of car inspection switch and the pit emergency stop switch may also be connected in the safety chain. The opening of a single hoistway door contact will break a connection between the power supply and the drive motor, and prevent movement of the car as long as the hoistway door is open.
During a normal stop at a floor, the hoistway door and the elevator car doors will open for a short period of time to allow passengers to enter or exit the elevator car. The doors will then close again, and the safety chain is closed so that the car can move in the hoistway to its next stop.
If a hoistway door is opened manually when a car is not in position adjacent that hoistway door (i.e. an abnormal opening of the hoistway door has occurred), the safety system will prevent normal operation of the elevator until a latch condition caused by the abnormal opening is safely cleared. The safety system operates on an assumption that whenever an abnormal opening of a hoistway door occurs, a person or persons could have entered the elevator hoistway. To prevent possible injury of authorized or unauthorized personnel that may have entered the hoistway while the hoistway door was open, the elevator system enters a shutdown condition that prevents elevator motion until a special sequence is followed. In the past, when a safety shutdown condition has occurred, a resetting of the elevator system to normal operation has required a manual reset by service personnel. Requirement of a manual reset by service personnel ensures that the elevator system is safe, with no personnel located in the hoistway, before operation resumes. It does, however, result in increased service costs. In addition, in some buildings, disabling the elevator until an onsite reset by service personnel can be performed is inconvenient and problematic. For example, losing the use of an elevator in a hospital for an extended period of time can be a problem when patients need to be moved from floor to floor.
Not every opening of a hoistway door results in persons remaining within the hoistway. For example, elevator inspectors may open a hoistway door briefly as part of the normal inspection. This opening of hoistway door by an inspector can generate a shutdown condition that requires a mechanic to visit the site to verify that there is no one in the hoistway and that normal elevator operation is safe to resume.
Examples of systems using elevator hoistway safety chains are described in U.S. Pat. No. 6,223,861 by Frank M. Sansevero entitled “Elevator Hoistway Access Safety”; U.S. Pat. No. 6,603,398 by Helio Tinone and Frank W. Adams entitled “Hoistway Access Detection System”; U.S. Pat. No. 6,467,585 by Michael Gozzo, Robert G. Morgan and Alberto Vecchiotti entitled “Wireless Safety Chain For Elevator System”; and U.S. Pat. No. 6,550,585 by Wolfgang M. Schoppa and Axel Steffen Gerwing entitled “Hoistway Intrusion Detection”. All of these patents are assigned to Otis Elevator Company. The Sansevero U.S. Pat. No. 6,223,861 allows the elevator car to move at an inspection speed when an opening of a hoistway door occurs unaccompanied by opening of a car door. The Tinone et al. U.S. Pat. No. 6,603,398 describes a hoistway access detection system using multiple safety chains. The Gozzo et al. U.S. Pat. No. 6,467,585 uses wireless transceivers associated with safety chain components to provide a wireless safety chain.
The Schoppa et al. U.S. Pat. No. 6,550,585 describes a safety system for elevators that includes motion sensors to detect movement of persons within the hoistway. When a safety shutdown has occurred as a result of an abnormal opening of a hoistway door, the safety control system will automatically reset the elevator to a normal operating state if the shaft monitoring device does not detect persons in the elevator hoistway during a predetermined period, such as 5 to 10 minutes. The shaft monitoring device may include an ultrasound or infrared motion sensor, video cameras connected to an image analyzer, or a load sensitive mat provided on top the car or in the hoistway pit.
U.S. Pat. No. 5,283,400 by Richard J. Leone, Robert F. Cummins, Joseph Vitiello, and Thomas Brochhagan entitled “Elevator Shaftway Intrusion Device” also describes an intrusion detector mounted on an elevator cab to detect unauthorized access to the top of elevator cars. The intrusion detector senses disturbance of an energy field by an intruder entering a zone of detection. The energy field may be electromagnetic energy within an infrared, radio frequency, or microwave frequency bands, or sonic energy in an ultrasonic frequency band.
U.S. Pat. No. 6,202,797 by Steven M. Skolnick, Chester J. Slabinski, and Frank M. Sansevero entitled “Automatic Protection of Elevator Mechanics” and assigned to Otis Elevator Company describes a safety system in which an elevator mechanic wears a portable device such as a transmitter when in the hoistway pit or on top of a car. Sensing devices on the top and bottom of the car are activated by the portable device to cause an emergency stop and to warn the mechanic.